The Kremlin on Friday slammed NATO and Ukraine for misinterpreting a remark by President Vladimir Putin as a virtual admission of Russian troops in eastern Ukraine.

The Russian president on Thursday once again denied the presence of regular Russian troops in Ukraine but admitted that some people have been carrying out military tasks there.

"We never said there weren't people (in Ukraine) who work on resolving various issues there, including in the military sphere," Putin said during his annual news conference.

Many -- including the president of Ukraine and the head of NATO -- interpreted Putin's words as effectively an acknowledgement that Russia did send regular troops across the border to buttress Russian-speaking rebels in eastern Ukraine, a claim the Kremlin has always denied.

NATO head Jens Stoltenberg, speaking as he met Ukrainian President Petro Poroshenko at NATO headquarters in Brussels, said on Thursday that Putin's remarks confirmed what the US-led military alliance believed all along -- that Russia had a military presence in eastern Ukraine.

Poroshenko, for his part, added: "Today the president of Russia for the first time publicly admitted the presence of Russian military in the occupied eastern part of Ukraine."

But Kremlin spokesman Dmitry Peskov said on Friday that these interpretations of Putin's comments were "completely erroneous."

Peskov said Putin was referring to Russian volunteers that had joined pro-Kremlin rebels in their fight against government troops in eastern Ukraine.

"These are the people who expressed their solidarity with the Donbass, who considered it unacceptable to put up with the Ukrainian armed forces destroying the populated areas of southeast Ukraine."

Putin's comment on the "military sphere" referred to the war in eastern Ukraine, Peskov said.

"People went there to fight, they shot and took part in fighting -- that is what the 'military sphere' is," he said.

Over the past few months, fighting between Kiev's forces and pro-Russian separatists in eastern Ukraine has largely died down although sporadic clashes still occur.

The UN last week hailed a "sharp de-escalation of hostilities" since the warring sides signed a new truce on September 1 in a conflict that has claimed more than 9,000 lives.

Putin last year acknowledged that Russian troops were in Crimea before Moscow seized the Black Sea peninsula from Ukraine, after initially denying it.